Psoriasis is a hyperproliferative disease of the skin, whose etiology is unknown. The skin lesions associated with psoriasis may be described as dull red patches or plaques of scaly erythema. The scales are distinctive, having a slightly opalescent silvery appearance. The disease has a predilection for certain areas of the body; thus the scalp, the extensor surfaces of the extremities (particularly at the elbows and knees), the back and the buttocks are most usually affected. However, the nails, eyebrows, axillae, umbilicus and anogenital regions are also frequent sites of involvement.
To date, there has been no report of a complete and permanent cure for psoriasis, and although the several treatments of choice available afford temporary remission of the symptoms, recurrence is almost certain. Most treatments involve the topical application of steroid (e.g. the adrenocortical steroids) ointments and creams, and no clinically successful, long-term, systemic treatment for the disease is currently available.